Contactor



p 1942- L. J. GOLDBERG 2,297,352

CONTACTOR Filed March 26, 1941 plg' MAGNETIC NON HAGNE TIC Inventor: Leon J. Goldberg,

HIS Attovney.

Patented Sept. 29, 1942 CONTACTOR Leon J. Goldberg, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application March 26, 1941, Serial No. 385,254

2 Claims.

My invention relates to contactors, particularly to time delay contactors such as used in the starting of electric motors, and has for its object a simple and reliable shim which may be adjusted with respect to the magnetic core members so as to provide an effective air gap in the magnetic circuit of widely varying length.

In carrying out my invention in one form, I provide a composite shim made of magnetic and non-magnetic materials, preferably iron and copper, so arranged that by means of an adjustment provided for the shim, an air gap of widely varying length or thickness can be provided as desired. More particularly I provide a shim having a non-magnetic portion made of non-magnetic material and a magnetic portion made of layers of magnetic and non-magnetic materials which is adjustably mounted, for example about a pivot, so that varying relative amounts of the two materials can be interposed in the magnetic circuit thereby to vary the length of the effective air gap. An important advantage of my invention is that the shim may be of uniform thickness so that, regardless of its adjustment, the relative positions of the core parts in the magnetic circuit remain the same.

Thus by using a composite shim embodying my invention in a time delay contactor, the contactor can be adjusted without partial disassembly of the contactor and by means of an easy and convenient adjustment from an accessible position on the contactor. Heretofore, it has been the practice to adjust the air gap by substituting a shim having a different thickness which requires partial disassembly of the contactor and also results in a change in the relative positions of the core members.

For a more complete understanding of my invention, reference should be had to the accompanying drawing, Fig. 1 of which is a view in section of a time delay contactor such as used in the starting of electric motors embodying my invention; Fig. 2 is a plan view of a shim embodying my invention; Fig. 3 is a sectional view of Fig. 2 along the line 33 and looking in the direction of the arrows; while Fig. 4 is a simplified diagram of an electric motor starting system utilizing the contactor shown in Fig. 1.

Referring to the drawing, I have shown my invention in one form as applied to a time delay contactor HI mounted on a suitable panel or support I I. This contactor is provided with an operating coil l2 and-withadock-out coil IS. It is provided with an armature l4 pivotally mounted on a knife-edged bearing support I! and suitably biased by gravity to the unattracted position shown in Fig.1 The armature I4 is attraotedby the magnetic core I6 extending through coil 12;; the magnetic circuit for the coil l2 completed by a core member I1.

An extension l8 made of magnetic material is provided on the armature Hi, the right-hand end of this extension as seen in thedrawing overlapping the end of a core member l9 extending across the outer end of the coil I3. A central core member 20 extends through the coil I! in engagement with the core member l9 and also in engagement with the core member I! and secured to it. Thus the magnetic flux path for the coil I3 when the coil (2 is energized, which is ordinarily the'case, is through the central core 20, the cores I9 and i8, the armature l4, and the central core l6 back to the core 20. Also, some of the magnetic flux set up by the coil 13 will return through the core member I! and a substantial portion of the flux produced by the coil I! will flow through the parallel flux path afforded by the central core 20 and the cores l9 and [8.

The coils l2 and I3 are so wound relative to each other that the coil l3 when energized holds the end of the core member l8 in engagement with the core member [9 against the pull applied to the armature H by the coil l2 until the excitation of the coil l3 has been reduced to a relatively low value.

The contactor thus far described is of the type described and claimed in a copending application of Benjamin W. Jones, Ser. No. 326,405, filed March 28, 1940 for Control systems, assigned to the same assignee as this application.

The contactor is provided with a conventional arc chute 2|. The coils and core members are supported on the panel II by means of brackets 22 and 23.

In accordance with my invention, I provide an adjustable shim 24 between the overlapping ends of the core members I8 and H by means of which the effective air gap between these two core members can be adjusted thereby to vary the lock-out holding force of the coil IS on the core member 3 and the armature I4. As shown in Figs. 2 and 3, this shim is in the form of a disc of uniform thickness provided with a central adj'ustment pivot aperture 25. The disc is formed of a non-magnetic material, preferably copper, with the exception of one half of one side, i. e., a semi-circular layer portion 26 at the top as seen in Fig. 3, which is made of a magnetic material, preferably iron. Preferably, this layer 26 has a thickness equal to about one half of the total thickness of the disc although obviously this dimension can be varied as desired.

The disc is pivotally secured, as shown in Fig. 1, to the core member, is by means of a screw 21 extending through the hole 25 in the disc in such a position that a portion of it on the left-hand side of the screw, as seen in Fig. 1, extends between the overlapping portions of the core members It and i9. Byloosening the screw 21, the disc shim can be turned to the desired position and then secured by tightening the screw. It will be observed that if the non-magnetic half 28 of the shim made entirely of copper extends between the two core members, then an effective air gap of maximum length is provided between the core members. When the bimetal or magnetic half of the shim extends between the core members, an eifective air gap of a desired minimum length, i. e., equal to the thickness of the layer of copper, is provided. Any desired eifective length of air gap between these two limits can be obtained by adjusting the position of the shim about its pivot to give the required proportions of the copper half 28 and the composite half of the shim between the two core members.

It will be observed that the screw 2? is easily accessible for adjustment of the shim and, moreover, because of the uniform thickness of the shim, the positions of the armature I 3 and the core member it remain unchanged with respect to the other parts of the device regardless of the angular position of the shim.

Another important advantage of my shim is that besides changing the amount of magnetic reluctance between the members l8 and I9 the shim also changes the distribution of the flux passing from one member to the other. Thus the flux tends to concentrate in the portion of the shim having the lower reluctance lying between the members [8 and Hi. This is important because a given amount of flux concentrated produces more pull than the same amount of flux distributed over a wider area. Thus the shim provides two means of obtaining the desired adjustment, i. e., by change in the effective length of the air gap and by change in the distribution of the flux.

Although I have shown the shim as mounted for adjustment about a pivot, it will be understood that it may be arranged for adjustment in various ways to bring the desired proportions of the magnetic and non-magnetic halves between the core members. For example, the shim may be slidably mounted for adjustment.

Referring to Fig. 4 as applied to the starting of an electric motor 29 provided with a starting resistance 39, the holding coil i2 is connected across the supply mains and also the lock-out coil I3 is connected across the supply mains. To provide a time delay interval, a suitable condenser 3! is connected in parallel with the lock-out coil I 3. In the starting of the motor when the switch 32 is opened as by the closing of a preceding contactor or by a manually operated controller, the lock-out coil I3 is disconnected from the supply source and the condenser 3i which has been charged by the supply source discharges through the look-out coil. The condenser discharge maintains energy in the lock-out coil is sufiiciently to hold the armature id in its unattracted position against the closing force applied by the coil I2 for a predetermined interval of time after which the coil i3 is disabled so that armature M is picked up and the contactor closed thereby closing a switch 33 and short-circuiting the starting resistance 30 in the motor circuit.

Thus by properly adjusting the position of the shim 2% about its pivot, the time during which the switch 33 is held open after the switch 32 is opened can be adjusted over a wide range.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination in a contactor, of a magnetic core member, an armature member for said core mounted for movement into engagement with said core member, a spacing disc having a single layer portion made of non-magnetic material and a composite portion made of layers of, respectively, non-magnetic and magnetic material, means pivotally mounting said disc at its center on one of said members so that a portion of said disc on one side of its center extends between said armature and core members, said disc being of uniform thickness whereby said armature and core members are maintained a predetermined distance apart by said disc, and said disc being rotatable on said mounting means to a position to bring the non-magnetic portion of said disc between said armature and core members for a maximum efiective air gap between them and rotatable from said position to bring gradually said composite portion between said members thereby gradually to decrease said efiective air gap until said composite portion is between said core portions for the minimum efiective air gap between them, a coil on said core for biasing when energized said armature member toward said core member so that said members are separated by said disc, and means for biasing said armature member to another position.

2. The combination in a contactor, of a magnetic core member, an armature member for said core movably mounted with relation to said core and arranged to engage said core member, a spacing shim made principally of non-magnetic metal in the form of a disc, means pivotally mounting said shim at its center on one of said members so that said .shim on one side of its center extends between said armature and core members, said shim having a portion of decreased thickness of non-magnetic metal, a layer of magnetic metal secured to said portion so as to form therewith a bimetal portion consisting of two layers of, respectively, non-magnetic and magnetic metals, said shim being of uniform thickness whereby said armature and core members are maintained a predetermined distance apart by said shim, and said shim bein rotatable on said mounting means to a position with the non-magnetic metal portion of said disc between said armature and core members for a maximum efl'ective air gap between them and rotatable from said position to bring said bimetal portion between said armature and core members thereby gradually to decrease said effective air gap until said bimetal portion is between said core portions for the minimum effective air gap between them, a coil on said magnet core for biasing when energized said armature member toward said core member, and means for biasing said armature to another position.

LEON J. GOLDBERG. 

